This invention is generally directed to hydroxygallium phthalocyanines and photoconductive imaging members thereof, and, more specifically, the present invention is directed to processes for the preparation of hydroxygallium phthalocyanines, including new crystalline forms thereof, by mixing hydroxygallium phthalocyanine Type V with an aliphatic alcohol, and wherein the alcohol is preferably methanol, ethanol, propanol, or butanol. More preferably, in embodiments the propanol is isopropanol, and the butanol is n-butanol. The photogenerating hydroxygallium phthalocyanine pigments resulting possess in embodiments a wide range of photosensitivities and with an E.sub.1/2 of about 2 to 75 ergs/cm.sup.2. The Type V hydroxygallium phthalocyanine can be prepared by a number of processes such as the formation of a precursor gallium phthalocyanine with, for example, an X-ray powder diffraction trace having peaks at Bragg angles 2.THETA. of 7.6, 8.1,9.7, 16.0, 18.4, 19.2, 19.9, 24.7, 25.7 and 26.2, and the highest peak at 8.1 degrees, prepared by the reaction of 1,3-diiminoisoindolene with gallium acetylacetonate in a suitable solvent, such as N-methylpyrrolidone, or halonaphthalene like 1-chloronaphthalene, quinoline, and the like; hydrolyzing the precursor by dissolving in a strong acid and then reprecipitating the resulting dissolved pigment in aqueous ammonia, thereby forming Type I hydroxygallium phthalocyanine; and admixing the Type I formed with a hydrophobic solvent of, for example, hexanes, including 1-hexanes and/or isomers thereof, heptane, cyclohexane, cyclopentane or esters, such as propylacetate, butylacetate, or ketones such as methyl isobutyl ketone, methyl isoamyl ketone, or toluene, and thereafter azeotropically removing water therefrom. In embodiments, the Type V can be prepared by the formation of a precursor prepared by the reaction of 1 part gallium acetylacetonate with from about 1 part to about 10 parts and preferably about 4 parts of 1,3-diiminoisoindolene in a solvent, such as quinoline, chloronaphthalene, or N-methylpyrrolidone, in an amount of from about 10 parts to about 100 parts and preferably about 19 parts, for each part of gallium acetylacetonate that is used, to provide a pigment precursor gallium phthalocyanine, which is subsequently washed with a component, such as dimethylformamide to provide the precursor gallium phthalocyanine as determined by X-ray powder diffraction, with an X-ray powder diffraction trace having peaks at Bragg angles 2.THETA. of 7.6, 8.1, 9.7, 16.0, 18.4, 19.2, 19.9, 24.7, 25.7, and 26.2, and the highest peak at 8.1 degrees; dissolving 1 weight part of the resulting gallium phthalocyanine in concentrated, about 94 percent, sulfuric acid in an amount of from about 1 weight part to about 100 weight parts and in an embodiment about 5 weight parts by stirring the pigment precursor gallium phthalocyanine in the acid for an effective period of time, from about 30 seconds to about 24 hours, and in an embodiment about 2 hours at a temperature of from about 0.degree. C. to about 75.degree. C., and preferably about 40.degree. C. in air or under an inert atmosphere, such as argon or nitrogen; adding the resulting mixture to a stirred organic solvent in a dropwise manner at a rate of about 0.5 milliliter per minute to about 10 milliliters per minute and in an embodiment about 1 milliliter per minute to a nonsolvent, which can be a mixture comprised of from about 1 volume part to about 10 volume parts and preferably about 4 volume parts of concentrated aqueous ammonia solution (14.8N) and from about 1 volume part to about 10 volume parts, and preferably about 7 volume parts of water for each volume part of acid like sulfuric acid that was used, which solvent mixture was chilled to a temperature of from about -25.degree. C. to about 10.degree. C. and in an embodiment about -5.degree. C. while being stirred at a rate sufficient to create a vortex extending to the bottom of the flask containing the solvent mixture; isolating the resulting blue pigment by, for example, filtration; and washing the hydroxygallium phthalocyanine product obtained with deionized water by redispersing and filtering from portions of deionized water, which portions are from about 10 volume parts to about 400 volume parts and in an embodiment about 200 volume parts for each weight part of precursor pigment gallium phthalocyanine which was used. The product, a dark blue solid, was confirmed to be Type I hydroxygallium phthalocyanine on the basis of its X-ray diffraction pattern having major peaks at Bragg angles 2.THETA. of 6.9, 13.1, 16.4, 21.0, 26.4, and the highest peak at 6.9 degrees. The Type I hydroxygallium phthalocyanine product obtained as a wet cake, approximately 10 percent by weight pigment and 90 percent by weight water, can then be dried by azeotropically distilling off water with a hydrophobic solvent, such as hexane, of from 1 part to 30 parts of wet cake to 100 parts by volume of solvent, preferably 20 parts. Water is removed by heating to the azeotrope boiling point and continued until the distillate temperature reaches the boiling point of the hydrophobic solvent. Further, in embodiments there can be selected as a reactant an alkoxy gallium phthalocyanine dimer, reference U.S. Pat. No. 5,521,306, U.S. Pat. No. 5,466,796 and U.S. Pat. No. 5,456,998 the disclosures of which are totally incorporated herein by reference.
In Bull Soc Chim. Fr., 23 (1962), there is illustrated the preparation of hydroxygallium phthalocyanine via the precursor chlorogallium phthalocyanine. The precursor chlorogallium phthalocyanine is prepared by reaction of o-cyanobenzamide with gallium chloride in the absence of solvent. O-cyanobenzamide is heated to its melting point (172.degree. C.), and to it is added gallium chloride at which time the temperature is increased to 210.degree. C. for 15 minutes, and then cooled. The solid is recrystallized out of boiling chloronaphthalene to give purple crystals having carbon, hydrogen and chlorine analyses matching theoretical values for chlorogallium phthalocyanine. Dissolution in concentrated sulfuric acid, followed by reprecipitation in diluted aqueous ammonia, affords material having carbon, and hydrogen analyses matching theoretical values for hydroxygallium phthalocyanine.
In JPLO.221459, there are illustrated gallium phthalocyanine compounds which show the following intense diffraction peaks at Bragg angles (2 theta +/-0.2.degree.) in the X-ray diffraction spectrum,
1--6.7, 15.2, 20.5, 27.0
2--6.7, 13.7, 16.3, 20.9, 26.3 (hydroxygallium phthalocyanine Type I)
3--7.5, 9.5, 11.0, 13.5, 19.1, 20.3, 21.8, 25.8, 27.1, 33.0 (chlorogallium phthalocyanine Type I).
Further, there is illustrated in JPLO.221459 a photoreceptor for use in electrophotography comprising a charge generation material and charge transport material on a conductive substrate, and the charge generation material comprising one or a mixture of two or more of gallium phthalocyanine compounds which show the following intense diffraction peaks at Bragg angles (2 theta +/-0.2.degree.) in the X-ray diffraction spectrum,
1--6.7, 15.2, 20.5, 27.0
2--6.7, 13.7, 16.3, 20.9, 26.3
3--7.5,9.5,11.0,13.5,19.1,20.3,21.8,25.8,27.1,33.0.
In U.S. Pat. No. 5,473,064, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of hydroxygallium phthalocyanine Type V, essentially free of chlorine, whereby a pigment precursor Type I chlorogallium phthalocyanine is prepared by reaction of gallium chloride in a solvent such as N-methylpyrrolidone with 1,3-diiminoisoindolene (DI.sup.3); hydrolyzing the pigment precursor chlorogallium phthalocyanine Type I by standard methods, for example acid pasting, whereby the pigment precursor is dissolved in concentrated sulfuric acid and then reprecipitated in a solvent, such as water, or a dilute ammonia solution; and subsequently treating the resulting hydrolyzed pigment hydroxygallium phthalocyanine Type I with a solvent, such as N,N-dimethylformamide by, for example, ball milling said Type I hydroxygallium phthalocyanine pigment in the presence of spherical glass beads, approximately 1 millimeter to 5 millimeters in diameter, at room temperature, about 25.degree. C., for a period of from about 12 hours to about 1 week, and preferably about 24 hours such that there is obtained a hydroxygallium phthalocyanine Type V ball milling contains very low levels of residual chlorine of from about 0.001 percent to about 0.1 percent.
Further, in U.S. Pat. No. 5,482,811, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of hydroxygallium phthalocyanines which comprises hydrolyzing a gallium phthalocyanine precursor pigment by dissolving said hydroxygallium phthalocyanine in a strong acid and then reprecipitating the resulting dissolved pigment in basic aqueous media; removing any ionic species formed by washing with water, concentrating the resulting aqueous slurry comprised of water and hydroxygallium phthalocyanine to a wet cake; removing water from said slurry by azeotropic distillation with an organic solvent; and subjecting said resulting pigment slurry to mixing with the addition of a second solvent to cause the formation of said hydroxygallium phthalocyanine.
In copending application U.S. Ser. No. 537,714, the disclosure of which is totally incorporated herein by reference, there are illustrated photoresponsive imaging members with photogenerating titanyl phthalocyanine layers prepared by vacuum deposition. It is indicated in this copending application that the imaging members comprised of the vacuum deposited titanyl phthalocyanines and aryl amine hole transporting compounds exhibit superior xerographic performance with low dark decay characteristics and high photosensitivity, particularly in comparison to several prior art imaging members prepared by solution coating or spray coating, reference for example U.S. Pat. No. 4,429,029 mentioned hereinbefore.
The invention hydroxygailium phthalocyanines obtained can be selected as organic photogenerator pigments in layered photoresponsive imaging members with charge transport layers, especially hole transport layers containing hole transport molecules such as known tertiary aryl amines. The aforementioned photoresponsive, or photoconductive imaging members can be negatively charged when the photogenerating layer is situated between the hole transport layer and the substrate, or positively charged when the hole transport layer is situated between the photogenerating layer and the supporting substrate. The layered photoresponsive imaging members can be selected for a number of different known imaging and printing processes including, for example, electrophotographic imaging processes, especially xerographic imaging and printing processes wherein negatively charged or positively charged images are rendered visible using toner compositions of appropriate charge polarity. In general, the imaging members are sensitive in the wavelength region of from about 550 to about 900 nanometers, and in particular, from about 660 to about 850 nanometers, thus diode lasers can be selected as the light source. The xerographic electrical properties of the imaging members can be determined by known means, including as indicated herein electrostatically charging the surfaces thereof with a corona discharge source until the surface potentials, as measured by a capacitively coupled probe attached to an electrometer, attained an initial value V.sub.o of about -800 volts. After resting for 0.5 second in the dark, the charged members attained a surface potential of V.sub.ddp, dark development potential. Each member can then be exposed to light from a filtered Xenon lamp with a XBO 150 watt bulb, thereby inducing a photodischarge which resulted in a reduction of surface potential to a V.sub.bg value, background potential. The percent of photodischarge was calculated as 100.times.(V.sub.ddp -V.sub.bg)/V.sub.ddp. The desired wavelength and energy of the exposed light was determined by the type of filters placed in front of the lamp. The monochromatic light photosensitivity was determined using a narrow band-pass filter. The photosensitivity of the imaging members is usually provided in terms of the amount of exposure energy in ergs/cm.sup.2, designated as E.sub.1/2 required to achieve 50 percent photodischarge from the dark development potential. The higher the photosensitivity, the smaller is the E.sub.1/2 value.
Layered photoresponsive imaging members have been described in a number of U.S. Patents, such as U.S. Pat. No. 4,265,900, the disclosure of which is totally incorporated herein by reference, wherein there is illustrated an imaging member comprised of a photogenerating layer, and an aryl amine hole transport layer. Examples of photogenerating layer components include trigonal selenium, metal phthalocyanines, vanadyl phthalocyanines, and metal free phthalocyanines. Additionally, there is described in U.S. Pat. No. 3,121,006 a composite xerographic photoconductive member comprised of finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder. The binder materials disclosed in the '006 patent comprise a material which is incapable of transporting for any significant distance injected charge carriers generated by the photoconductive particles.
The disclosures of all of the aforementioned publications, laid open applications, copending applications and patents are totally incorporated herein by reference.